In operando investigation of GaN PIN device characteristics under electron irradiation energies comparable to Pm-147 source for betavoltaic application

Abstract

Here, we report on the application of an electron source with high accelerating voltage (62 kV–200 kV) to simulate betavoltaic power generation capabilities of a planar GaN PIN (p-GaN/i-GaN/n-GaN) device. The in situ electrical characterization reported here enables detailed performance comparison of new device designs to conventional device configurations. In operando investigation of a GaN PIN device under irradiation by a modified transmission electron microscope is being reported here. A large-area planar GaN PIN (0.04 cm2, 17.8 nA/cm2 at 5 V reverse bias) device was irradiated with an electron beam of approximately equivalent spot size. At an approximate input current density of 5 nA/cm2, the maximum power produced (MPP) decreases from 2.45 µW/cm2 to 0.45 µW/cm2 with an increase in the beam voltage from 62 kV to 200 kV. This reduction in power corresponds to reduced electron–hole pair generation and capture within the active region of the device. The inverse relation of MPP to beam voltage is modeled by CASINO2 Monte Carlo simulations of energy absorption and is found to be in good agreement with the experimental measurement. At a constant 62 kV beam voltage, MPP is shown to increase with beam current density up to 48.2 µW/cm2 at 177 nA/cm2. Repeated device dark current measurements following the irradiation indicate no degradation of the device. An irradiation dose of ∼1016 cm−2, equivalent to exposure from a 10 mCi radioisotope source for 1 yr, was performed at an energy of 200 kV, with no appreciable deterioration in device performance.